(a) Field of the Invention
The present invention concerns a process for the production of at least one gas component from a gas mixture containing the gas component to be produced, comprising the steps of sending a flow of the gas mixture under a first pressure through a device for separation by adsorption to give, during a production stage, substantially at the first pressure, the gas component, and, during a stage of desorption-elution, at a second pressure lower than the first pressure, a first residual gas, and raising the pressure of the first residual gas to combine same with a flow of auxiliary gas.
(b) Description of Prior Art
In the processes of this type, the intent is to valorize the residual gas and the most simple manner, since this residual gas generally contains combustible gases, is to add same to an auxiliary network of combustible gas, so-called "fuel-gas" network, which is generally available on site, since, for example for the preparation of pure hydrogen, the process is generally associated with an appended apparatus of a petrochemical complex or a petroleum refinery, where such "fuel-gas" network recovers different purged gases, for example hydrodesulfurization purged gases available under high pressure and which are expanded at substantially lower pressures, for example of the order of 5 to 6.times.10.sup.5 Pa, through a simple valve, and which constitutes the service pressure of the "fuel-gas" network. Hereinafter, in the present patent application, the pressure of this "fuel-gas" network or more generally of a network of auxiliary gas is designated average pressure, since it is currently located between the high cycle pressure and the low cycle pressure of the adsorption unit for preparing the gas component. As a matter of fact, and notwithstanding the pressure of the gas component, typically in hydrogenated form, to be treated in the adsorption unit, it would be of the upmost interest to utilize a low cycle pressure which would be as low as possible, since the gas component yield of the adsorption unit--which is represented by the ratio of the volume of the gas component produced to the volume of the gas component in the initial mixture--is more particularly elevated, the lower the low pressure of the cycle, which results, without giving more complicated details, from a better desorption, therefore a better regeneration of the adsorbent of the adsorption unit and it is not rare that for this purpose a process is close to atmospheric pressure, sometimes below atmospheric pressure. It should be understood that it is not therefore simply possible to add this residual gas under this low pressure directly to the "fuel-gas" network under "mean" pressure.
Depending on cases, this residual gas is added by correspondingly raising the low cycle pressure, to the detriment of the yield of the gas component produced, or by utilizing a compressor, which enables to maintain the yield of the gas component produced, but constitutes a costly solution in equipment and maintenance expenses, as well as in consumption of energy.